1. Field of the Invention
The present invention relates to an electromagnetic relay, and more specifically to an electromagnetic relay having a permanent magnet and an armature block pivotally supported at roughly the middle portion thereof.
2. Description of Prior Art
Japanese Patent Kokai (Laid Open) Publication No. 61-218030 discloses an example of prior-art electromagnetic relays, in which an electromagnetic block, a permanent magnet and an armature block are arranged within a housing composed of a base and a casing. The electromagnetic block has an iron core formed into roughly U-shape and with a pair of bent opposing magnetic poles at both the ends thereof and a coil wound around the iron core via a spool. The permanent magnet is disposed between the two magnetic poles with both ends facing the magnetic poles magnetized in the same pole and with the middle portion magnetized in the opposite pole. The armature block is pivotally supported at the middle portion of the permanent magnet with both the ends thereof positioned so as to oppose the magnetic poles, respectively.
In the above-mentioned prior-art electromagnetic relay, however, there exist various problems as follows:
(a) A bonding process is required to fix the permanent magnet onto the electromagnetic block.
(b) Since the movable contacts provided for the armature block and the fixed contacts disposed on the base and opposing the movable contacts are brought into contact with or separated from each other via the electromagnetic block, the permanent magnet bonded to the electromagnetic block and the armature block pivotally supported on the permanent magnet, gap between the fixed contacts and the movable contacts are not uniform, thus resulting in dispersion in dynamic characteristics of the magnetic relay.
(c) Since the electromagnet block, the permanent magnet, and the armature block are disposed one upon another, the height of the relay is inevitably increased, thus increasing the size of the electromagnetic relay.